1,1-dimethoxy-2,5-dimethyl hexane



United States Patent Int. (:1. C07c 4'3/14 U.S. Cl. 260615 1 ClaimABSTRACT OF THE DISCLOSURE 1,l-dimethoxy-2,5-dimethyl hexane which isuseful as an odorant in the preparation of perfumes and other scentedpreparations.

CROSS REFERENCE TO RELATED APPLICATIONS This application is a divisionalapplication of Ser. No. 688,378, filed Dec. 6, 1967, now U.S. Patent3,428,694, which is a continuation-in-part of Ser. No. 380,927, now U.S.Patent No. 3,381,039.

DETAILED DESCRIPTION OF THE INVENTION The compound of this invention isa derivative produced by the acetalization and/ or catalytichydrogenation of 'y, d-unsaturated aldehydes having the general formulaRi-( ]=(i1CHz-GHCHO I in which R represents a hydrocarbon residue or anoxygen-containing hydrocarbon residue; R represents a lower alkyl group;and wherein R and R taken together, represent a carbocyclic radical; Rrepresents a hydrogen atom or a lower alkyl group and R represents ahydrogen atom or lower hydrocarbon residue.

Representative of the hydrocarbon residues which, in Formula I, aredepicted by the symbol R are saturated aliphatic hydrocarbon residueshaving from 1 to 16 carbon atoms and unsaturated aliphatic hydrocarbonresidues having from 2 to 16 carbon atoms. In a preferred embodiment ofthe invention, the cymbol R represents an alkyl or alkenyl group havinga straight or branched chain, such as, a methyl, ethyl, propyl,isopropyl, butyl, isobutyl group or a group having the formula 3 L 2h]nin which 11 presents an integer from 1 to 3, and wherein the broken linerepresents an optional double bond.

Additionally, the symbol R as it appears in Formula I, represents alkyland alkenyl groups, of the type mentioned heretofore, havingoxygen-containing substituents. Thus, for example, R represents ahydrocarbon residue having free, esterified and etherified hydroxygroups, oxo groups or free or esterified carboxyl groups. The esterifiedhydroxy groups include, for example, acyloxy groups, the acyl residue ofwhich is derived from a lower aliphatic or aromatic carboxylic acid,such as, formic acid, acetic acid, propionic acid, butyric acid, etc.,or benzoic acid. The etherified hydroxy groups include, for example,lower alkoxy groups, such as, methoxy, ethoxy, propoxy, isopropoxy,etc., radicals; or aryloxy groups, such as a phenoxy radical. Asexamples of esterified carboxyl groups there can be mentioned carbalkoxygroups, the alkyl component of which is derived from a lower alkanol,such as, methanol, ethanol, propanol, etc. Additional examples of thegroups represented by the symbol R in Formula I 3,493,621 Patented Feb.3, 1970 "ice are aromatic or araliphatic residues, such as, phenylbenzyl, phenethyl, etc. radicals, as well as derivatives of suchradicals having oxygen-containing substituents. The latter derivativesinclude aromatic and araliphatic residues which contain free, etherifiedor esterified hydroxy groups or free or esterified carboxyl groups.

The symbol R which appears in Formula I, represents an alkyl grouphaving from 1 to 8 carbon atoms, such as, ethyl, propyl, butyl, pentyl,hexyl, etc. A preferred group of compounds of the invention contain,however, a methyl group as the R substituent. The symbol R which appearsin Formula I, represents a hydrogen atom or an alkyl group having, forexample, from 1 to 3 carbon atoms, such as, an ethyl or propyl radical,However, the preferred compounds of the invention contain a methyl groupas the R alkyl substituent.

Representative of the lower hydrocarbon residues which, in Formula I,are represented by the symbol R are alkyl, cycloalkyl, aryl, and aralkylgroups having from 1 to 8 carbon atoms, such as, methyl, ethyl, propyl,cyclohexyl, allyl, pentyl, phenyl, benzyl, etc. radicals.

Additionally, R and R of Formula I, when taken together, represent aring structure, such as a S-member or a 6-member carbocyclic radical.For example, R and R taken together, represent a tetramethylene orpentamethylene group.

In the practice of this invention the starting aldehydes of Formula Iwhich are, in a first step of the process, either aoetalized to producean vat-unsaturated acetal of the following formula:

or hydrogenated to yield an aldehyde having the following formula:

Formula. II are hydrogenated or the aldehydes of Formula III areacetalized to yield a compound having the formula In Formulas II, IIIand IV, the symbols R R and R have the same meaning as in Formula I. Thesymbol R which appears in Formulas II and IV represents a lower alkylgroup, e.g., an alkyl group having from 1 to 6 carbon atoms or a loweralkenyl group, e.g., an alkenyl group having from 2 to 6 carbon atoms;taken together, the two symbols R represent a lower alkylene group.

The preferred compounds of Formula IV contain as the R substituents,lower alkyl groups, such as, methyl, ethyl, propyl, butyl, etc., groups.The lower alkylene group, which is represented by the symbols R and Rinclude ethylene, trimethylene, tetramethylene, etc., radicals.

Acetalization of the aldehydes of Formula I or Formula III is effectedin a known manner. In general, the acetalization is carried out in thepresence of hydrogen ions, with the separation of the water which forms.The requisite hydrogen ion concentration can be provided, for example,by the use of acid catalysts, such as, anhydrous mineral acids;p-toluene sulphonic acid; cation exchangers, such as, phenol-resinsulphonic acids; ammonium chloride; zinc chloride; pyridinehydrochloride; sodium hydrogen sulphate; ferric chloride, borontrifluoride etherate; etc. The water, which is formed during the courseof the reaction, can be removed from the reaction mixture by azeotropicdistillation or by the addition of a waterbinding agent, such as, anorthosilicic acid ester, an

orthoformic acid ester, 2,2-dimethoxy-propane or dimethyl sulphite.Acetalization, which is effected by the reaction by the aldehyde ofFormula I or III with an alcohol, especially a lower molecular weightprimary alcohol, in admixture with orthoformic acid ethyl ester, hasbeen found to be a convenient preparative step. In producing a dimethylacetal or a dipropyl acetal, it has been found advisable to use anexcess of the alcohol reactant, that is, methanol or propanolrespectively, in an excess amount to avoid the formation of the diethylacetal. Thus, for example, in the preparation of a dimethyl acetal ordipropyl acetal, it is preferred to use a large excess of alcohol,namely, from about to about 20 moles of alcohol per mole of aldehyde.Acetalization of the aldehyde using a glycol, particularly usingethylene glycol, is effected quite readily, even in the absence of awater-binding agent.

In the hydrogenation step of the present process, one can use anycatalyst which is normally used for the selective hydrogenation of theolefin bond of carbonylcontaining olefins. Suitable for use as thecatalyst, are, for example, palladium and Raney nickel. Using such acatalyst, the t-unsaturated aldehydes of Formula I are converted to thealdehydes of Formula III which are saturated in the 'y,6-position. Thehydrogenation reaction is continued until such time as a calculatedtheoretical amount of hydrogen has been absorbed by the reactionmixture. If desired, the quantity of hydrogen used may be suflicient tohydrogenate also any other olefinic bonds, present in the aldehyde. In apreferred preparative method, acetone is used as a solvent for thereaction and a finely divided palladium oxide-palladium hydroxidemixture on carbon is used as the catalyst.

Hydrogenation of the acetals of Formula II is readily effected. Since itis well known that an acetal group is quite resistant to the reaction ofthe reducing agents, there can be used as the hydrogenation catalyst, inaddition to palladium and Raney nickel, catalysts which are lessselective in their activity. In all other respects, the hydrogenation ofan acetal compound of Formula II can be effected in the conventionalmanner, at atmospheric pressure or higher.

The aldehydes of Formula I, which are used in the starting material inthe practice of this invention, can be prepared by the acid-catalyzedreaction of a tertiary allyl alcohol of the formula ing as in Formula Iwith an aldehyde enol ether of the formula in which R, has the samemeaning as in Formula I and R represents a lower alkyl group. Thisreaction is effected with the splitting off of one mole of the alcoholrepresented by the formula R OH, in which the symbol R has the samemeaning as in Formula VI.

The novel compounds of Formulas II, III and IV have valuable andparticularly useful properties. Because of their fine and, at times,unusual fragrance, the compounds are useful as odorants in thepreparation of the perfumes and other scented preparations. In general,the compounds are characterized by a natural flowery note. The acetalsof Formulas II and IV are especially useful for the perfuming of soapand other cosmetic preparations.

For a fuller understanding of the nature and objects of this invention,reference may be had to the following examples which are given merely asillustrations of the invention and are not to be construed in a limitingsense.

4 EXAMPLE 1 A solution of 140 mg. of p-toluenesulphonic acid in 280 ml.of methanol was added to a mixture of 28 grams of 5-methyl-4-hexen-l-aland 37 grams of orthoformic acid ethyl ester. The reaction wasexothermic, the temperature of the reaction mixture reaching 33 C. Afterstanding for a period of two hours, the reaction mixture was treatedwith 1.4 grams of sodium acetate and concentrated in a 50 C.-bath at 35mm. Distillation of the residue, in vacuo, yielded1,1-dimethoxy-5-methyl-4-hexene, boiling point at 89 C. at 35 mm.; n=1.4294. The compound has a characteristic fruit-like green odor.

EXAMPLE 2 A mixture of 112 grams of 5-methyl-4-hexene-1-al, 62 grams ofethylene glycol and 0.2 gram of p-toluenesulphonic acid was distilled at50 mm. in a 100 C.-bath. A major portion of water present therein wasthus removed. Thereafter, the pressure was reduced to 12 mm. and therewas thus obtained 1,1-ethylenedioxy-5-methyl-4-hexene[=1-(1,3-dioxolan-2-yl)-4-methyl-3-pentene] as a colorless oil which waspurified by repeated distillation. This compound had a boiling point atC. at 12 mm.; n :l.4512. The compound had an odor resembling 5-methyl-l-hexanal, but much finer.

EXAMPLE 3 63 grams of 2,5-dimethyl-4-hexen-l-al were mixed with 640 ml.of methanol, 75 grams of orthoformic acid ethyl ester and 1.5 ml. ofboron trifluoride etherate. After 30 minutes the mixture was treatedwtih 3 ml. of triethylamine and a fore-run was first distilled off at 13mm. in a 50 C.-bath. Thereafter, there was obtained from a C.-bath,1,1-dimethoxy-2,5-dimethyl-4-hexene which was purified byredistillation. This compound, boiling point at 77 C. at 13 mm. and /z=1.4343, had a harsh, fruitlike green odor.

EXAMPLE 4 63 grams of 2,5-dimethyl-4-hexene-1-al were mixed with 46grams of ethanol, 75 grams of ortho-formic acid ethyl ester and 1.7 ml.of boron trifluoride etherate. The temperature of the reaction mixturerose, oxothermically, to 60 C. After two hours, the mixture wasneutralized with 3.4 ml. of triethylamine and a fore-run was firstdistilled off at 14 mm. in a 50 C.-bath. Thereafter, 1,1-diethoxy-2,5-dimethyl-4-hexene was distilled oft in a C.-bath. Thecompound, boiling point at 92 C. at 14 mm. and n =1.432l, had an odorsimilar to that of 1,1- dimethoxy-2,5-dirnethyl-4-hexene, but distinctlyfiner.

EXAMPLE 5 63 grams of 2,5-dimethyl-4-hexen-l-al were mixed with 650 ml.of n-propyl alcohol and 75 grams of orthoformic acid ethyl ester. Thereaction was initiated by the addition of 1.5 ml. of boron trifluorideetherate. After two hours, 300 ml. of the reaction was evaporated off ina 120 C.-bath, following which the portion of the reaction mixtureremaining was neutralized with 3 ml. of triethylarnine. A fore-run wasthereafter separated at 13 mm. in a 100 C.-bath. Subsequently,1,1-di-n-propoxy-2,5-dimethyl-4- hexene was distilled off using toC.-bath. The compound, thus obtained, had a boiling point of 113 to 114C. at 13 mm. and rz =1.4358. It had an odor which was finer and moreflowery than 1,l-diethoxy-2,5-dirnethyl- 4-hexene.

EXAMPLE 6 63 grams of 2,5-dimethyl-4-hexen-l-al were mixed with 700 ml.of n-butanol and 75 grams of orthoformic acid ethyl ester. Thereafter,1.5 ml. of boron trifluoride etherate was added to the mixture and itwas allowed to stand for a period of two hours, during which time thetemperature thereof rose, exothermically, to 33 C. A 350 ml. of afore-run was then distilled off in a 70 C.-bath at 13 mm.

That portion of the reaction mixture which remained behind wasthereafter neutralized with 3 ml. of triethylamine. A second fore-runwas separated off in a 100 C.-bath at 13 mm. and, subsequently,1,1-di-n-butoxy-2,S-dimethyl- 4-hexene was distilled off in high vacuum.That compound, which had a boiling point at 70 C. at 0.015 mm. and n1.4392, had a fresh-flowery, faint odor.

EXAMPLE 7 A mixture of 126 grams of 2,5-dimethyl-4-hexene-l-al, 62 gramsof ethylene glycol and 0.18 gram of p-toluene sulphonic acid was firstprepared. Water was distilled from this mixture at 50 mm. in a 100C.-bath. Thereafter, the bath-temperature was increased to 130 C. andthe 1,1- ethylenedioxy-2,5-dimethyl-4-hexene which was thus formed, wasdistilled off. The compound had a boiling point of 120 C. at 50 mm. andn =1.453l. It had a fruit-like green odor with a fine cacao-likeside-note.

EXAMPLE 8 A mixture of 180 g. of 5,9-dimethyl-4,8-decadien-l-al, 62grams of ethylene glycol and 0.25 gram of p-toluenesulphonic acid wasdistilled, first in a 120 C.-bath at 13 mm. and then in high vacuum.There was thus obtained 1,l-ethylenedioxy-5,9-dimethyl 4,8 decadiene,boiling point at 91 C. at 0.02 mm. and n =l.4738. This compound had apleasant mellow odor, reminscent of that of5,9-dimethyl-4,8-decadien-1-al, but is significantly finer and milder.

EXAMPLE 9 EXAMPLE 10 56 grams of 2-pentyl-5-isobuty1-4-hexen-l-al in 23grams of ethanol and 38 grams of orthoformic acid ethyl ester weretreated with 1 ml. of boron trifluoride etherate and worked up after 2hours. There was thus obtained, 1,1 diethoxy 2 pentyl 5 isobutyl 4hexene, boiling point at 98 C. at 0.08 mm. and n =1.4452, having afaintly fatty odor.

EXAMPLE 1 1 A mixture of 46 grams of 5-methyl-7-acetoxy-4-heptenl-al,15.5 grams of ethylene glycol and 60 mg. of ptoluene sulphonic acid wasmaintained at 13 mm. in a 120 C.-bath. Thereafter, the1,l-ethylenedioxy-S-methyl- 7-acetoxy-4-hepten, which was thus formedwas recovered by distillation in high vacuum. The compound, having aboiling point of 92 C. at 0.05 mm. and n =1.4628, had a faint, freshodor.

EXAMPLE 12 42.5 grams of 5,9-dimethyl-9-methoxy-4-decen-l-al in 20 gramsof ethanol and 30 grams of orthoformic acid ethyl ester were treatedwith 1 ml. of boron trifiuoride etherate and worked up after a period ofabout two hours. There was, thus obtained, 1,1-diethoxy-5,9-dimethyl-9-methoxy-4-decene, boiling point at 105 C. at 0.07 mm. and n =l.4476,having a smoky, faintly flowery-fatty odor.

EXAMPLE 13 28 grams of 5-methyl-4-hexen-1-al were mixed with 140 ml. ofacetone. Thereafter, the mixture was treated with 2.8 grams of 5 percentpalladium-carbon (finely divided palladium oxide-hydroxide mixture oncarbon). Such mixture was then shaken for a period of 15 hours in ahydrogen atmosphere. During the reaction, about 5.5 liters of hydrogenwere taken up. Subsequently, the reaction mixture was filtered under anatmosphere of nitrogen gas to remove the catalyst therefrom and theacetone was distilled off in a 50 C.-bath at mm. The crude5-methyl-1-hexanal, thus obtained, was purified by distillation. Thecompound, boiling point at 84 C. at 100 mm. and n =1.4104, had a strong,fruitlike odor.

EXAMPLE 14 31.5 grams of 2,5-dimethyl-4-hexen-l-al were dissolved in 150ml. of acetone, treated with 3.1 g. of a palladiumcarbon catalyst,identical to that described in Example 13, and the mixture was shaken ina hydrogen atmosphere. Approximately 2.5 liters of hydrogen were takenup within one hour. Thereafter, an additional 3.1 grams ofpalladium-carbon catalyst were added to the mixture, under an atmosphereof nitrogen gas, and the hydrogenation was continued for a period of 8hours. During that time an additional 3 liters of hydrogen were takenup. There was, thus obtained, 2,5-dimethyl-1-hexanal, boiling point at47 C. at 13 mm. and n =1.4142, having a fine and fruit-like odor.

EXAMPLE 15 45 grams of 5,9-dimethyl-4,8-decadien-1-a1 in 220 ml. ofacetone were hydrogenated by the procedure described in Example 14.About 11 liters of hydrogen were taken up. Pure 5,9-dimethyl-1-decanalwas obtained after the usual working up and distillation in high vacuum.The compound, boiling at 55 C. at 0.06 mm. and n =1.4348, had a typicalaldehyde long lasting odor with a new and interesting note.

EXAMPLE 16 38 grams of 4-cyclohexylidene-l-butanal in 200 ml. of acetonewere hydrogenated, two times, using 3.8 grams of palladium-carboncatalyst, by the method described in Example 14. About 5.5 liters ofhydrogen were taken up. The desired 5-cyclohexyl-1-butanal was obtainedas a colorless oil after the usual working up and distillation in highvacuum. The compound, having a boiling point at 55 C. at 0.15 mm. and n=1.4595, had a complex odor which was fruit-like green and faintlyaldehydic.

EXAMPLE 17 25 grams of 5,9-dimethyl-9-hydroxy-4-decen 1 al in 150 m1. ofacetone were hydrogenated in the presence of 2.5 grams of 5 percentpalladium-carbon catalyst as described in Example 13. About 3 liters ofhydrogen were taken up. There was thus obtained 5,9 dimethyl 9-hydroxy-l-decanal as a color-less oil after the usual working up anddistillation in high vacuum. The compound had a boiling point at 99 C.at 0.04 mm. and n =1.4573 and a faint, but pleasant, fresh-flowery odor.

EXAMPLE 18 26.5 grams of 5,9-dimethyl-9-methoxy-4-decen-l-al in 150 ml.of acetone were hydrogenated in the presence of 2.6 grams of 5 percentpalladium-carbon catalyst, as described in Example 13. About 3 liters ofhydrogen were taken up. After the customary working up, there wasobtained 5,9-dimethyl-9-methoxy-l-decanal, boiling point at 78 C. at0.03 mm. and n =1.4442. The compound had a fine and flowery odor.

EXAMPLE 19 (a) 32 grams of 2,5-dimethyl-1-hexanal, produced as describedin Example 14, were worked up by the method of Example 1 with 37 gramsof orthoformic acid ethyl ester, 280 ml. of methanol and mg. ofp-toluene sulphonic acid. There was thus obtained, 1,1-dimethoxy-2,5-dimethyl-hexane, boiling point at 72 C. at 13 mm. and n =1.4154,having a flowery, slightly fruit-like green odor.

3,493,621 7 8 (b) The same compound Was obtained by the hydro- 2,962,53411/ 1960 Montagna et a1. genation of 1,1-dimethoxy-2,5-dimethy1-4-hcxeneby the 3,010,997 11/1961 Robinson et a1.

process described in Example 13. The starting 1,1-di- 3,121,120 2/1964Montagna et a1. methoxy-Z,5-dimethyl-4-hexene was produced as describedI claimi West et 211.: Synthetic Perfumes, Edward Arnold & 1.1,1-d1.methoxy-2,5-d1methyl-hexane. c London, 1949 31 References CitedLEON ZITVER, Primary Examiner UNITED STATES PATENTS 10 H. T. MARS,Assistant Examiner 2,853,529 9/1958 Hcrrmann.

